Precise Positioning with GPS & GLONASS:
Performance Evaluation on the UNSW Campus

With the continuing development of Global Navigation Satellite Systems (GNSS) there are constantly new satellites, systems and developments coming online. Currently there are only two systems that are in operational stages: the United States’ NAVSTAR Global Positioning System (GPS) and Russia’s Global’naya Navigatsionnya Sputnikovaya Sistema (GLONASS).There will be another two systems added to this infrastructure in the foreseeable future with the European Union deploying Galileo and China establishing Compass.


The increased number of satellites and signals combined with the better signal structures that are being implemented are expected to have an impact on the accuracy and precision of measurements obtained from GNSS receivers. The question however remains as to what affect these changes will have and will they improve accuracies in areas previously thought to be unsuitable for GNSS observations such as dense urban environments.


Many precise GNSS positioning techniques such as Real-Time Kinematic (RTK) and rapid static baselines have been widely used for geodetic and surveying applications. The accuracies achievable by these methods are highly dependant on the number and geometry of the observed satellites. The more satellites observed, the better the precise GNSS positioning performance. It has been noted that in some built-up areas, such as the UNSW campus, the effective use of GNSS for these types of precise positioning is constrained. To improve the performance of these precise GNSS techniques multiple GNSS are being used simultaneously.

 

Several GNSS manufacturers, such as Leica Geosystems, NovAtel, Topcon and Trimble have developed new GNSS products that can track and process the measurements from both GPS and GLONASS satellites. This projects aims to use one commercial GNSS product to compare GPS only and combined GPS GLONASS solutions for both RTK and rapid static scenarios over the UNSW campus control network.

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